<template>
  <div class="pagination">
    <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">
      上一页
    </button>
    <button
      v-if="startNum_endNum.start > 1"
      @click="$emit('getPageNo', 1)"
      :class="{ active: pageNo == 1 }"
    >
      1
    </button>
    <button v-if="startNum_endNum.start > 2">···</button>
    <template v-for="(page, index) in startNum_endNum.end">
      <button
        :key="index"
        @click="$emit('getPageNo', page)"
        :class="{ active: pageNo == page }"
        v-if="page >= startNum_endNum.start"
      >
        {{ page }}
      </button>
    </template>

    <button v-if="startNum_endNum.end < totalPage - 1">···</button>
    <button
      v-if="startNum_endNum.end < totalPage"
      @click="$emit('getPageNo', totalPage)"
      :class="{ active: pageNo == totalPage }"
    >
      {{ totalPage }}
    </button>
    <button
      :disabled="pageNo == totalPage"
      @click="$emit('getPageNo', pageNo + 1)"
    >
      下一页
    </button>
    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>
<script>
export default {
  name: "Pagination",
  props: ["pageNo", "pageSize", "total", "continues", "totalPage"],
  computed: {
    // 连续页码的起始数字与结束数字【连续页码的数字：至少是5】
    startNum_endNum() {
      const { continues, pageNo, totalPage } = this;
      let start = 0,
        end = 0;

      if (totalPage) {
        // 不正常现象【总页数没有连续页码多】
        if (continues > totalPage) {
          start = 1;
          end = totalPage;
        } else {
          start = pageNo - parseInt(continues / 2);
          end = pageNo + parseInt(continues / 2);
          //start数字出现0|负数
          if (start < 1) {
            start = 1;
            end = continues;
          }
          //end数字大于总页码
          if (end > totalPage) {
            end = totalPage;
            start = totalPage - continues + 1;
          }
        }
      }

      return { start, end };
    },
  },
};
</script>
<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active {
  background: skyblue;
}
</style>